Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Suzuki GSX 750 1981 start issues

Discussion in 'Technical and Troubleshooting Torque' started by veom, Feb 22, 2013.

  1. Hey guys,

    A mate and I recently bought a Suzuki GSX 750 it was run down and in a mess. We have cleaned it up a little but it won't start. So far we have cleaned the carbs and replaced the plugs. We've tested spark on all 4 cyclinders and all the carbs seem to be getting fuel into the float bowl. The battery is pretty good and cranks it over. We tried spraying some "start ya basted" into the carb air intake, when we did we got some combustion but it only seemed to fire once or twice then stopped.

    We aren't really sure what the next step could be? We are planning on checking the compression in each cylinder, but I think the issue could be fuel delivery. Does anyone have any ideas or things to try/check to get her going?

    We've mixed some of the coils around after reading the manual. They seem to be in the correct place now, after using start ya bastard again in the carb in take the engine will fire up to really high rpm around (6000) then it will shut off. I suspect the carbs aren't delivering fuel.

    Are there any ways of testing to see if the carbs are in fact delivering fuel?

  2. Make sure you've got the coils connected to the correct cylinders. Swap them and you might get the odd gurgle and fart but the engine will never start. If it were fuel delivery, I'd expect the engine to actually run for a few seconds on a decent squirt of ether, not just cough a bit. Given fuel and a spark at the correct moment, the engine should run as long as it's got enough compression to be felt by a thumb over the plug hole. Low compression, unless it's catastrophic across all cylinders, generally won't stop an engine from showing some sign of life. Power and fuel economy are another matter.

    Has the previous owner recently had the cams out? Unlikely as the GSX has, IIRC, screw and locknut tappets, but I've seen inlet and exhaust cams swapped over in the past. An engine with this problem, though, would show little compression in the thumb test and would also be blowing back through the carbs, both of which you'd notice, along with possible unpleasant mechanical noises as valves and pistons kissed.
  3. Turn it over for a few seconds with the choke on. Then take a plug out. If fuel is getting through but the engine hasn't fired, the plug will be visibly wet with petrol.
  4. Does that model use points in the ignition system? If so, that's a good place to look.

    Even if it doesn't, whatever type of ignition advance you have there might still be off.